Security door



FIG. 1 is a top plan view of a security door showing our new design the bottom being a mirror image thereof;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a left end elevational view thereof;

FIG. 4 is a rear elevational view.

The broken line showing of the structural indicia is for illustrative purposes only and forms no part of the claimed design. 

The ornamental design for a security door, as shown and described. 